Writing and reading data having multiple access patterns on tape media

ABSTRACT

Data is recorded such that the positions of data will be aligned in a traveling direction and a width direction of the storage medium. The medium travels in the traveling direction from a first to a second position as a certain wrap of a group of plural files in a first physical range between the first and the second positions. A head shifts from the certain wrap to another wrap in the width direction of the medium. The medium travels in the traveling direction from a third to a fourth position as the other wrap of a group of plural files in a second physical range between the third and the fourth positions. The plural files in groups on the certain wrap and the other wrap may be written in reverse order to each other after being once stored in a buffer.

The present patent application is a DOMESTIC COUNTERPART of, and claimspriority under PCT to, the foreign patent application No. 2013-224185filed in Japan on Oct. 29, 2013.

TECHNICAL FIELD

The present invention relates to a method of writing and reading datahaving multiple access patterns on a tape medium.

BACKGROUND ART

IBM (IBM is a trademark of International Business Machines Corporationregistered in many countries around the world) has a product called LTFS(Linear Tape File System) as a file system that runs on a tape device.

Some versions can be downloaded for free from a web site as software ora program cooperating with hardware, and other versions are sold.

LTFS is an open standard, and multiple companies are doing business withproducts adopting the LTFS standard.

FIG. 1 is a schematic diagram of usages of data bands and wraps on atape medium adopting an LTO (Linear Tape-Open) as a conventionaltechnique.

The tape medium adopting the LTO standard is divided into areas calledfour data bands as in FIG. 1.

When a tape drive writes data to the tape medium, the tape drivereciprocates a tape with a total length of a few hundred meters a fewdozen times to write an amount of data corresponding to the prescribedcapacity of the tape medium.

Although simplified in FIG. 1, the tape is actually reciprocated aboutten times per data band (the number of reciprocations differs dependingon the generation of the format).

This one way is called a “wrap.”

All wraps are numbered. The wraps used to read and write data whiletraveling the tape medium in the forward direction have even numbers,and the wraps used to read and write data while traveling the tapemedium in the backward direction have odd numbers.

When writing data and when reading written data serially, the tapemedium can read and write data at a transfer rate of about 160 MB/sec.

On the other hand, when plural pieces of data existing in any positionsare read, since the length of the tape medium is about 800 m, a seektime of one minute on average or about two minutes at most is requiredfor the travel between pieces of data.

In other words, when discrete pieces of multiple data existing at anypositions are read, the transfer rate is significantly reduced. It canbe said that the cause is the seek time required.

The emergence of LTFS enables users of tape media to write and readfiles to and from the tape media directly via a file system withoutthrough dedicated backup software or a hierarchical storage system.

Therefore, more and more users who did not use tape media in the pasthave begun using the tape media.

In a hospital, various kinds of data that range from data of a smallsize, such as name, sex, and age in an electronic medical record or thelike, to data of a large size, such as an X-ray image or video takenwith an endoscope are used.

Although it has been conventionally common practice to manage such kindsof data in a hard disk drive (HDD), the introduction of LTFS to managedata is being considered because the threshold to use tape media throughthe LTFS has been lowered.

As the characteristics of data handled in a hospital, multiple methodsof using data exist.

As an access pattern used in medical examination and treatment, there isa pattern of access to plural kinds of data (e.g., name, sex, age, anX-ray image, and endoscopic video) in units of patients.

On the other hand, as an access pattern for academic use, there is apattern of access to specific data (e.g., X-ray images) across multiplepatients.

When random access occurs in data reading, the transfer rate in datareading is significantly reduced irrespective of whether the storagedestination of data is a tape medium or an HDD.

Thus, there is a reduction in reading transfer rate caused by randomaccess that occurs when there are multiple access patterns for usingdata.

Patent Literature 1 is made by the same applicant as this application,and it is meaningful as a reference to understanding a writing methodadopted as a prerequisite in the present invention.

In Patent Literature 1, data are written by paying attention only to onerectangle (a singular file of each of name, sex, age, X-ray image, andendoscopic video) as shown in FIG. 6 of the present application (to bedescribed in detail later) only to intend to read data vertically.

To summarize a difference between (features of) Patent Literature 1 andthe present invention, the present invention also considers alandscape-oriented rectangle as shown in FIG. 5 of the presentapplication to write data to a tape medium in a manner to make it easyto read the data along both the landscape orientation (along thelandscape-oriented rectangle) and the portrait orientation (along theportrait-oriented rectangle).

In other words, in the present invention, data are written by payingattention to two-dimensional arrangement on the assumption of use inmultiple access patterns.

[Patent Literature 1] Japanese Patent Application Publication No.2013-191259

SUMMARY OF INVENTION

The purpose of the present invention is to solve a problem of areduction in reading transfer rate caused by random access that occurswhen there are multiple methods of using data.

In the present invention, data to be recorded on a storage medium are sorecorded that the positions of data will be aligned in a travelingdirection of the storage medium (in a longitudinal direction in the caseof a tape medium) and a width direction of the storage medium accordingto each of multiple data access patterns to reduce the required seektime at the time of data reading in order to improve the transfer ratein data reading.

According to the present invention, the required seek time is reduced atthe time of data reading, and this can improve the transfer rate in datareading. Specific numeric values will be described later.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram of usages of data bands and wraps on atape medium as a conventional technique.

FIG. 2 is a diagram showing a configuration example of a file systemrelated to the present invention.

FIG. 3 is a diagram showing a configuration example of a tape driverelated to the present invention.

FIG. 4 is a diagram showing a method of recording data having multipleaccess patterns as the present invention.

FIG. 5 is a diagram showing the movement of a tape medium as the presentinvention when data on patient 0 recorded on the tape medium are read.

FIG. 6 is a diagram showing the movement of the tape medium as thepresent invention when all X-ray images recorded on the tape medium areread.

FIG. 7 is a diagram showing a conventional technique when partialinformation on each patient is read from written data using aconventional method.

FIG. 8 is a diagram showing a recording method when multiple pieces ofpatient information are recorded in the lateral direction.

DETAILED DESCRIPTION

An embodiment of the present invention will be described with referenceto the accompanying drawings.

FIG. 2 is a diagram showing a configuration example of a file systemrelated to the present invention.

A file system 100 is made up of a tape drive 10, a host (server) 30, andPCs (terminals) 32 and 34, which are communicable with one anotherthrough a network 36.

Although the tape drive 10 and the host (server) 30 are each illustratedas one component in FIG. 2, this is just an example, and two or moretape drives 10 and hosts (servers) 30 can be included.

Further, though not shown, an external data source is connectable to thenetwork 36 so that data can be sent to the tape drive 10 directly orthrough the server 30 and the PC 32, 34.

For example, the file system 100 can be an LTFS (Linear Tape FileSystem).

Like an HDD, a USB memory, or any other removable recording medium suchas a CD-R, the LTFS provides a mechanism that enables direct access to afile stored in a tape cartridge when the tape cartridge is inserted intothe tape drive.

In order to build a file system on a tape medium, the tape drive needsto have a partition feature.

In LTO standards after LTO-5, a tape is divided into two partitions.

FIG. 3 is a diagram showing a configuration example of the tape driverelated to the present invention.

The tape drive 10 includes a host interface (hereinafter called “hostI/F”) 11, a buffer 12, a channel 13, a head 14, and a motor 15.

The tape drive 10 also includes a controller 16, a head position controlsystem 17, and a motor driver 18.

Since a tape cartridge 20 is loadable when the tape cartridge 20 isinserted into the tape drive 10, the tape cartridge 20 is further shownhere.

This tape cartridge 20 includes a tape 23 wound on reels 21 and 22.

The tape 23 moves in a longitudinal direction with the rotation of thereels 21 and 22 from the reel 21 to the reel 22 (forward direction) orfrom the reel 22 to the reel 21 (backward direction).

A magnetic tape is exemplified as the tape 23, but the tape 23 may beany storage medium (e.g., HDD) other than the magnetic tape.

The tape cartridge 20 also includes a cartridge memory (CM) 24. This CM24 records, for example, information about how data was written on thetape 23.

Then, for example, an index of data written on the tape 23 in anoncontact mode using an RF interface or the usage of the tape 23 ischecked to enable high-speed access to the data.

In FIG. 3, an interface like this RF interface for performing access tothe CM 24 is shown as a cartridge memory interface (hereinafter,referred to as “CM I/F”) 19.

Here, the host I/F 11 performs communication with the host (server) 30or the other PC 32.

For example, the host I/F 11 receives, from an OS of the host 30, acommand to instruct writing of data to the tape 23, a command to movethe tape 23 to a target position, and a command to instruct reading ofdata from the tape 23.

In the example of the LTFS mentioned above, data within the tape drivecan be referred directly from a desktop OS or the like, and a file canbe executed by the double click or copied by the drag-and-drop actionlike a case of handling a file within an HDD.

The buffer 12 is a memory for accumulating data to be written to thetape 23 and data read from the tape 23.

For example, the buffer 12 is a DRAM.

The buffer 12 is composed of multiple buffer segments, and each buffersegment stores a data set as a unit of read/write from/to the tape 23.

Data sent from the external data source through the network 36 in FIG. 2are accumulated sequentially in the buffer 12.

The channel 13 is a communication channel used to send the head 14 datato be written to the tape 23 and receive, from the head 14, data readfrom the tape 23.

The head 14 writes information to the tape 23 and reads information fromthe tape 23 when the tape 23 reciprocates in the longitudinal direction.

The motor 15 drives the reels 21 and 22 to rotate.

Note that although the motor 15 is indicated by one rectangle in FIG. 3,it is preferred to provide, as the motor 15, a total of two motors, onefor each of the reels 21 and 22.

The controller 16 controls the entire tape drive 10. For example, thecontroller 16 controls writing to the tape 23 and reading from the tape23 according to the commands accepted at the host I/F 11.

The controller 16 also controls the head position control system 17 andthe motor driver 18.

The head position control system 17 is a system for keeping track of adesired wrap.

The wrap is a group of multiple tracks on the tape 23 that the head 14can read and write at a time.

Although the number of wraps depends on the format of the tape 23, it istypically about several dozens.

The length (given length) of a wrap can be set by the controller 16.

When it is necessary to switch (move) from one wrap to another, the head14 also needs to be electrically switched. Such switching is controlledby this head position control system 17.

The head is shifted from a certain wrap to another wrap.

The motor driver 18 drives the motor 15.

As mentioned above, if two motors 15 are used, two motor drivers 18 willalso be provided.

The CM I/F 19 is, for example, implemented by an RF reader/writer towrite information to the CM 24 and read information from the CM 24.

The present invention will be described below by taking, as an example,a case where electronic medical records handled in a hospital are storedon a tape medium.

FIG. 4 is a diagram showing a method of recording data having multipleaccess patterns as the present invention.

In the present invention, when information on electronic medical recordsis recorded on a tape medium, the information is so recorded that datafor each patient will be aligned laterally and data for each kind willbe aligned longitudinally as shown in FIG. 4.

Specifically, a physical range of groups of multiple files stored acrossmultiple wraps divided in the width direction of a storage medium (thelateral direction of a tape medium or the radial direction of an HDD) isrecorded to align in the traveling direction of the storage medium (thelongitudinal direction of the tape medium or the rotational direction ofthe HDD).

In a specific procedure, the storage medium is traveled in the travelingdirection (longitudinal direction) from a first position to a secondposition of the storage medium as a certain wrap.

During this travel, a group of multiple files is written or the group ofmultiple files is read in a first physical range between the firstposition and the second position.

Next, the head is shifted from the certain wrap to another wrap in thewidth direction of the storage medium.

The storage medium is traveled in the traveling direction (longitudinaldirection) from a third position to a fourth position of the storagemedium as the other wrap.

During this travel, a group of multiple files is written or the group ofmultiple files is read in a second physical range between the thirdposition and the fourth position.

Here, when the traveling direction (longitudinal direction) of thestorage medium on the certain wrap and the traveling direction(longitudinal direction) of the storage medium on the other wrap areopposite to each other, writing to a wrap in the opposite direction canbe done in such a manner that, after the group of multiple files in theforward direction is once stored in the buffer, these multiple files arewritten in reverse order.

Further, the first physical range and the second physical range, andfurther the respective positions of the multiple files in these rangesare substantially aligned in the traveling direction (longitudinaldirection) of the storage medium.

It is a further feature that the group of multiple files on the certainwrap and the group of multiple files on the other wrap are provided in amanner to be distinguishable as access patterns (along the landscapeorientation) on a wrap-to-wrap basis.

Here, the attribute of each of the multiple files stored in the firstphysical range is substantially the same as the attribute of each of themultiple files stored in the second physical range.

Specifically, as information on electronic medical records in ahospital, the attribute of each of the multiple files is name, sex, age,X-ray image, or endoscopic video.

In practice, all the attributes are not necessarily required as datahandled in the hospital, but at least one of them will be included.

Further, the group of multiple files on the certain wrap and the groupof multiple files on the other wrap are provided in a manner to bedistinguished from each other data by data on personal information(e.g., for each patient).

Such a distinction is effective in terms of protecting personalinformation.

The certain wrap and the other wrap are reciprocated across patient 0 topatient N, and repeated alternately in the width direction of thestorage medium.

As shown, the certain wrap is set as an odd-numbered or even-numberedwrap as an outward path, and the other wrap is set as an even-numberedor odd-numbered wrap as a return path.

In order to match the data size per patient to the data capacity perwrap of the tape medium, the tape medium may be scaled (i.e., logicallyshortened to reduce the capacity), or conversely, the write startingpositions of respective data may be aligned by adding dummy data ontothe tape medium at the time of writing without being scaled.

Thus, it is necessary to grasp the size of each data beforehand in orderto perform recording, but this limitation is not a problem in such asituation that data are archived on a tape medium.

Applications using tape media including LTFS can use a SCSI commandcalled Request Sense to grasp to which portion on a tape medium thewrite end position of data corresponds.

When the capacities are not matched to each other, or when the recordingend position of each data is shifted by the compression function of atape drive, dummy data can be written to align the write startingpositions of respective data.

In other words, as a specific option, the storage medium may be scaled(i.e., logically shortened to reduce the capacity) to adjust the sizesof groups of multiple files stored across multiple wraps in order toalign the first position to the fourth position.

As another specific option, dummy data may be added at the time ofwriting groups of multiple files to adjust the sizes of groups ofmultiple files stored across multiple wraps in order to align the firstposition or the third position.

FIG. 5 is a diagram showing the movement of the tape medium as thepresent invention when data on patient 0 recorded on the tape medium areread.

The data is thus recorded. In this case, for example, when data on apatient are read for the purpose of medical examination and treatment,data are sequentially read as shown in FIG. 5 as one of access patternsto enable high-speed reading of the data.

FIG. 6 is a diagram showing the movement of the tape medium as thepresent invention when all X-ray images recorded on the tape medium areread.

When specific data are read for the purpose of academic use, data areread as shown in FIG. 6 as another access pattern to enable high-speedreading of the data.

For example, when it is desired to read videos of a certain age group,the ages of all patients are first read by the method shown in FIG. 6,and corresponding videos are then read. This can significantly reducethe required seek time that is the main factor of a reduction intransfer rate at the time of reading.

FIG. 7 is a diagram showing a conventional technique when partialinformation on each patient is read from written data using aconventional method.

When data are recorded using the conventional method without beingaligned in the longitudinal direction, there will be a need to performseek over an entire range of the tape and to move between arrows even ifportions to be actually read are only the portions indicated by thearrows in FIG. 7 in order to read X-ray images of all patients.

Therefore, if the wrap length is 800 m, the tape travel speed is 10m/sec, and the number of wraps is 100, the time required for readingwill be two hours or more (800 [m]/10 [m/sec]*100/60 [sec]/60 [min]=2.22. . . ).

On the other hand, assuming that the size of an X-ray image per patientis 1 GB and the transfer rate is 250 MB/sec, the required seek time whendata are aligned in the longitudinal direction is about 2 seconds atmost.

Thus, it can be said that X-ray images of all the patients can be readin about 10 minutes by the application of the present invention ((1000[MB]/250 [MB/sec]+2 [sec])*100/60 [sec]=10).

FIG. 8 is a diagram showing a recording method when multiple pieces ofpatient information are recorded in the lateral direction.

When the data size per patient is smaller than the capacity of the tapemedium, information on multiple patients can, of course, be arranged inthe lateral direction as shown in FIG. 8.

Specifically, a section corresponding to the first physical range and asection corresponding to the second physical range appear repeatedlyeven in different positions in the traveling direction (longitudinaldirection) of the storage medium.

While the application of the present invention to a tape medium as akind of storage medium has been described, the present invention is notlimited thereto.

Further, it goes without saying that those skilled in the art can adaptthe present invention to various directions of storage mediaaccordingly, such as the rotational direction or the radial direction ofa disk (an example of a storage medium) to be rotated in an HDD, and theseek direction of a head. The term “storage medium” does not encompass asignal propagation medium, any description in this disclosure to thecontrary notwithstanding.

1-10. (canceled)
 11. An apparatus for storing files, the apparatuscomprising: a storage medium on which physical ranges of groups ofplural files stored across a plurality of wraps divided in a widthdirection of the storage medium are aligned in a traveling direction ofthe storage medium, wherein the travelling direction of the storagemedium is a longitudinal direction of the storage medium, and whereinthe width direction of the storage medium is a lateral direction of thestorage medium, wherein as a result of traveling the storage medium inthe traveling direction from a first position to a second position ofthe storage medium as a certain wrap, a group of plural files is writtenin a first physical range between the first position and the secondposition, as a result of traveling the storage medium in the travelingdirection from a third position to a fourth position of the storagemedium as another wrap, a group of plural files is written in a secondphysical range between the third position and the fourth position, thefirst physical range and the second physical range, and further relativepositions of plural files in these ranges are substantially aligned inthe traveling direction of the storage medium, an attribute of each ofplural files stored in the first physical range is substantiallyidentical to an attribute of each of plural files stored in the secondphysical range, and the group of plural files on the certain wrap andthe group of plural files on the other wrap are provided in a manner tobe distinguishable from each other.
 12. The apparatus according to claim11, wherein a section corresponding to the first physical range and asection corresponding to the second physical range appear repeatedlyeven in different positions in the traveling direction of the storagemedium.
 13. (canceled)
 14. The apparatus according to claim 11, whereinstorage of a group of plural files as the certain wrap and storage of agroup of plural files as the other wrap are reciprocated withsubstantially identical attributes of groups of plural files, andrepeated alternately in the width direction of the storage medium. 15.The apparatus according to claim 14, wherein the certain wrap is anodd-numbered or even-numbered wrap as an outward path, and the otherwrap is an even-numbered or odd-numbered wrap as a return path.
 16. Theapparatus according to claim 11, wherein the storage medium is scaledfor the groups of plural files stored across the plurality of wraps toalign the first position to the fourth position, wherein when thestorage medium is scaled the storage medium is logically shortened toreduce a capacity.
 17. The apparatus according to claim 11, whereindummy data is added when the groups of plural files stored across theplurality of wraps are written to align the first position or the thirdposition.
 18. The apparatus according to claim 11, wherein the storagemedium is a tape medium, the traveling direction of the storage mediumon the certain wrap and the traveling direction of the storage medium onthe other wrap are opposite to each other, and an order in the group ofplural files on the certain wrap and an order in the group of pluralfiles on the other wrap are as a result of being written in reverseorder to each other.
 19. A system for aligning, in a traveling directionof a storage medium, physical ranges of groups of plural files storedacross a plurality of wraps divided in a width direction of the storagemedium, the system comprising: a first component to travel the storagemedium in the traveling direction from a first position to a secondposition of the storage medium as a certain wrap to write a group ofplural files or read the group of plural files in a first physical rangebetween the first position and the second position, wherein thetravelling direction of the storage medium is a longitudinal directionof the storage medium, and wherein the width direction of the storagemedium is a lateral direction of the storage medium; a second componentto shift a head from the certain wrap to another wrap in the widthdirection of the storage medium; a third component to travel the storagemedium in the traveling direction from a third position to a fourthposition of the storage medium as the other wrap to write a group ofplural files or read the group of plural files in a second physicalrange between the third position and the fourth position; a fourthcomponent to align the first physical range and the second physicalrange, and further relative positions of plural files in these rangessubstantially in the traveling direction of the storage medium, whereinan attribute of each of plural files stored in the first physical rangeis substantially identical to an attribute of each of plural filesstored in the second physical range; and a fifth component to providethe group of plural files on the certain wrap and the group of pluralfiles on the other wrap in a manner to be distinguishable from eachother.
 20. The system according to claim 19, wherein the storage mediumcomprises a tape medium, the tape medium is loaded in an Linear TapeFile System (LTFS) that runs on a tape device, the traveling directionof the storage medium on the certain wrap and the traveling direction ofthe storage medium on the other wrap are opposite to each other, and thesystem is operable to do writing to a warp in a backward direction insuch a manner that, after a group of plural files in a forward directionis once stored, these plural files are written in reverse order. 21.(canceled)
 22. (canceled)
 23. (canceled)
 24. (canceled)
 25. A computerreadable article of manufacture tangibly embodying a computer readableinstructions which, when executed, cause a computer to carry out stepsof a method for aligning, in a traveling direction of a storage medium,physical ranges of groups of plural files stored across a plurality ofwraps divided in a width direction of the storage medium, the methodcomprising: traveling the storage medium in the traveling direction froma first position to a second position of the storage medium as a certainwrap to write a group of plural files or read the group of plural filesin a first physical range between the first position and the secondposition, wherein the travelling direction of the storage medium is alongitudinal direction of the storage medium, and wherein the widthdirection of the storage medium is a lateral direction of the storagemedium; shifting a head from the certain wrap to another wrap in thewidth direction of the storage medium; traveling the storage medium inthe traveling direction from a third position to a fourth position ofthe storage medium as the other wrap to write a group of plural files orread the group of plural files in a second physical range between thethird position and the fourth position; aligning the first physicalrange and the second physical range, and further relative positions ofplural files in these ranges substantially in the traveling direction ofthe storage medium, wherein an attribute of each of plural files storedin the first physical range is substantially identical to an attributeof each of plural files stored in the second physical range; andproviding the group of plural files on the certain wrap and the group ofplural files on the other wrap in a manner to be distinguishable fromeach other.